利用尾波包络线反演方法研究2003年大姚地震震中区下方地壳的非均匀结构  

Imaging crustal heterogeneity in 2003 Dayao,Yunnan,earthquake region by inverting coda envelopes

作　　者：王勤彩[1] 陈章立[1] 郑斯华[1] 

机构地区：[1]中国地震局地震预测研究所,中国北京100036

出　　处：《地震学报》2010年第4期383-391,共9页Acta Seismologica Sinica

基　　金：国家科技支撑重点项目(2008BAC38B02);地震行业科研专项(200708026)资助

摘　　要：以单次散射模型、球形辐射源、一维线性速度模型为基础计算理论包络线,通过尾波归一化方法把理论与观测包络线结合起来形成非线性方程组,用迭代最小二乘方法反演大姚震区的散射系数空间分布.结果显示,MS6.2和MS6.1地震序列的主震和余震基本都分布在高散射系数区内.MS6.2地震序列震源深度在研究区中部向下弯曲绕过低散射系数区,在深度剖面上呈弧形分布;震源深度较浅的MS6.1地震序列向北西、南东方向的扩展终止于两端的低散射系数区.大姚强震区10km深度上的高散射系数条带沿震源断层分布,暗示了震区下方断层破碎带的存在.Synthetic envelopes are calculated on the basis of the single scattering theory,with the assumption of spherical radiation sources and a one-dimensional depth-dependent crust velocity model.An observation equation,which connects synthetic and observed energy densities,is obtained by employing coda normalization method.Finally,we obtain the spatial distribution of scattering coefficients in the Dayao earthquake region using a standard least squares technique iteratively.The results show that two main shocks and most aftershocks of the MS6.2 and MS6.1 earthquake sequences occurred within large scattering coefficient zones.On depth section,MS6.2 earthquake sequence bends downwards to round a low scattering coefficient zone and forms an arc shape in section.Focal depths of aftershocks of the MS6.1 earthquake are relatively shallow.The extension of MS6.1 earthquake sequence towards northwest and southeast ends at low scattering coefficient zones.The large scattering coefficient zones at depth of 10 km distribute along the main shock faults,impling that there are fault-damaged zones beneath the Dayao strong earthquake region.

关 键 词：大姚震区 散射系数 尾波包络线 地壳的非均匀结构 

分 类 号：P315.31[天文地球—地震学]